Apparatus for magnetic printing



Aug. 15, 1961 J. c. SIMS, JR

APPARATUS FOR MAGNETIC PRINTING 6 Sheets-Sheet 1 Original Filed April17, 1951 INVENTOR M asmw.

1961 J. c. SIMS, JR

APPARATUS FOR MAGNETIC PRINTING 6 Sheets-Sheet 2 Original Filed April17, 1951 INVENTOR Aug. 15, 1961 J. c. SIMS, JR

APPARATUS FOR MAGNETIC PRINTING 6 Sheets-Sheet 3 Original Filed April17, 1951 INVENTOR 1961 J. c. SIMS, JR

APPARATUS FOR MAGNETIC PRINTING 6 Sheets-Sheet 4 Original Filed April1-7, 1951 INVEN TOR a Jim/5 Afr:

J\ JL JL JL T /\/\/\f JUL/U Aug. 15, 1961 Q M JR 2,996,575

APPARATUS FOR MAGNETIC PRINTING Original Filed April 17, 1951 6 S eet 5IN VEN TOR Aug. 15, 1961 J. c. SIMS, JR 2,996,575

- APPARATUS FOR MAGNETIC PRINTING Original Filed April 17, 1951 6Sheets-Sheet 6 I N VEN TOR United States Patent 2,996,575 APPARATUS FORMAGNETIC PRINTING John C. Sims, Jr., Sudbury, Mass., assignor to SperryRand Corporation, New York, N.Y., a corporation of Delaware Continuationof application Ser. No. 221,362, Apr. 17,

1951. This application Apr. 27, 1960, Ser. No. 24,929

'13 Claims. (Cl. 178--6.6)

This invention relates to the art of printing and, more particularly, toa method of high speed printing utilizing magnetic principles. Thepresent application is a continuation of application Serial Number221,362, filed April 17, 1951, now abandoned, which application was asubstitute for the abandoned original application Serial Number 143,737filed on February 11, 1950.

In the prior art, one method of printing has been to provide meanswhereby elevated contacting surfaces have been used directly, orindirectly, as in the offset method, to transfer a marking substance toa receiving medium to effectuate printing. This method includes the useof pre-fabricated type faces registering letters and figures, includinghalftone pictorial representations, as well as moving type face printerswhich embrace gang printers, such as those where type is set up line byline in accordance with holes sensed on a punched paper card or tape.

The prefabrication of type faces is relatively time consuming andexpensive especially when but a few printed copies are desired. Althoughgang printing can be used advantageously when a few printed copies aredesired, its use does not extend to reproduction of pictorialrepresentations and is seriously handicapped by the relatively greatprinting time needed, as well as the costliness of the equipmentrequired.

Another well known printing process, known as facsimile, effectsregistration by passing electric currents through a special chemicallytreated paper. This technique is limited in its application to thereproduction of single printed copies, the printing time required andthe cost of electro-sensitive paper consumed being excessive for highspeed, low cost printing.

A recently developed process of printing makes use of a surfacecontaining electrically charged areas, to which a printing powder willadhere until removed by a receiving medium excited with a complementarycharge. The obvious disadvantages of such a procedure can be seen to beinherent in the necessity of recharging said surface area before eachprinting operation, and in the necessity of utilizing high electrostaticfield and charging potentials. Failure of this system under conditionsof high humidity is common.

Accordingly, one of the objects of the invention is to provide a new andimproved method of and apparatus for printing, adapted to low costreproduction of symbolic and pictorial representations.

Another object of the invention is to provide a new and improved methodof and apparatus for printing, adapted to high speed reproduction ofsymbolic and pictorial representations.

Still another object of the invention is to provide a new and improvedmethod of and apparatus for printing, adapted to allow the rapid settingup of any representations to be reproduced.

Yet another object of the invention is to provide a new and improvedmethod of and apparatus for printing, adapted to high quantityreproduction of symbolic and pictorial representations with a singlesetup of such material.

A further object of the invention is to provide a new and improvedmethod of and apparatus for printing, readily allowing unlimited changesin the representations ice set up for reproduction without involving aphysical reformation or replacement of the intelligence-bearingmaterial.

Still a further object of the invention is to provide a new and improvedmethod of and apparatus for printing on untreated commercially availablepapers.

Yet a further object of the invention is to provide a new and improvedapparatus for printing, utilizing an electronic scanning networkyielding a high signal to noise ratio.

Still another object of the invention is to provide a new and improvedmethod of and apparatus for printing, well adapted to printingintelligence derivable from an electrical signal source.

A further object of the invention is to provide a new and improvedmethod of and apparatus for printing, adapted to selectively produceeither positive or negative printed reproductions.

Another object of the invention is to provide a new and improvedapparatus for printing, having high operational efliciency andsimplified construction.

Yet another object of the invention is to provide a new and improvedapparatus for printing, which is inexpensive to construct and has a lowmaintenance cost.

Still another object of the invention is to provide a new and improvedmethod of and apparatus for printing adapted for operation without thenecessary utilization of electrostatic field and charging potentials.

A further object of the invention is to provide a new and improvedapparatus for printing adapted to singly satisfy all of the above statedobjects.

The advantages of the invention are developed in the method of printingcomprising the producing of a selected pattern of magnetic gradientsover the surface of a body, causing paramagnetic particles coming intocontact with said surface to be selectively retained thereon, andeffecting the transfer of at least a portion of such particles to animage-receiving medium.

The paramagnetic particles may, for example, be the powder of anymagnetic substance such as iron, nickel, or cobalt. Greater printingdefinition may be obtained by using the finer powders. However, to takefull advantage of their use, it may be found necessary to admix anon-magnetic powder having larger particles, as for example those foundin talcum powder, to prevent clumping of the finer magnetic particles.

The image-receiving medium, which can be ordinary paper or othermaterial, may be wetted by a solvent to more effectively receive theprinting particles, or may be sprayed with an adhesive substance toeffect a like purpose and provide a permanent bond. The particles alsomay be fixed by treatment after they have been received on the paper, byadministering a fixative at that time, by spraying.

In some instances it may be desirable to remove printing particles froma print-receiving web or sheet (textile, paper, wood, plastic, or othermaterial can be used) after they have been transferred thereto. Whenthat is the case, pigment-bearing particles may be used to color a paperpreviously sprayed with a solvent, at their points of contact therewith.Or the printing particles can be caused to react chemically to producecolor at the points of contact with a paper previously sprayed with asuitable reagent. vFor example, a print-receiving paper can bepreviously treated with potassium ferricyanide, K Fe(CN) to produceferrous ferrioyanide, commonly called Turnbulls blue, Fe [Fe(CN) byreacting with iron particles. By suitable combinations of reactingreagents and particles, a variety of printed colors may be produced.Paramagnetic particles can also be used as a catalytic agent to effectpigmentation of a reacting substance to produce similar results. Thenumerous other modes of effecting registration by the utilization ofparamagnetic particles will be apparent to those versed in the arts ofchemistry and/or printing.

Greatly diversified means can be utilized in carrying through the abovedescribed method. Although it appears desirable to utilize a body havingan easily magnetizable surface for the facile production of magneticgradients thereon, it is readily conceivable that the production ofmagnetic gradients can also be effected by arranging the poles ofnumerous small magnets to form a surface area, or by a similararrangement of numerous small electromagnets.

Likewise the generation of magnetic gradients over a magnetizablesurface is not limited to a particular scanning scheme but issusceptible of accomplishment by a great variety of means.

The transferring of particles from a magnetized surface can beaccomplished by use of a contacting means, as well as by use of anattracting field or other means.

The above and further objects and aspects of the invention will becomemore apparent from the following detailed description taken withreference to the accompanying drawings in which:

FIGURE 1 is a perspective view of a signal scanning and setup device,being part of a printing apparatus in accordance with the presentinvention,

FIGURE 2. is a fragmentary sectional view illustrating the constructionof an electromagnetic recording head producing tangential magneticfields, which may be embodied in the device of FIGURE 1,

FIGURE 3 is a fragmentary sectional view illustrating the constructionof another type of electromagnetic recording head producingsubstantially perpendicular magnetic fields, for use in the device ofFIGURE 1,

FIGURE 4 illustrates schematically an electronic signal transformingcircuit used in association with the device of FIGURE 1, adapted to thescanning of screened or uni-contrast representations,

FIGURE 5 illustrates schematically another electronic signaltransforming circuit usable in place of the circuit shown in FIGURE 4,being adapted to the scanning of multi-contrast or halftonerepresentations,

FIGURE 6 illustrates schematically a third electronic signaltransforming circuit usable in place of the circuit shown in FIGURE 5,

FIGURES 7, 8 and 9 are graphic representations of signals found invarious parts of the circuit illustrated in FIGURE 6, during differentconditions of excitation,

FIGURE 10 is a diagrammatic view, partially in section, of a printingunit, embodying the principles of the present invention,

FIGURE 11 is a schematic circuit of an opacity responsive control deviceused in connection with the ap paratus shown in FIGURE 10, and,

FIGURE 12 illustrates an apparatus for producing pigment-bearing ordye-coated magnetically attractable powdered particles which aresuitable for use in the up paratus shown in FIGURE 10.

Like reference characters identify like parts throughout.

Referring now to FIGURE 1 which shows the signal scanning unit, aphotoscanned cylinder 10 is adapted to receive around its circularperiphery a sheet of material containing representations to bereproduced in a printing process. The photoscanned cylinder 10 issupported by means of an axial shaft 11, which is connected at oneextremity to a shaft coupler 12 joined to a drive shaft 33, which isrotatably mounted in an end-bearing block 14. The other extremity ofaxial shaft 11 is joined to a coupler 16 and is rotatably mounted in acenter bearing block 13 having a removable cap 54 attached by a pair ofbolts 44.

'The photoscanned cylinder 10 is freely rotatable. Provision is alsomade for the easy replacement of said cylinder 10 by decoupling theaxial shaft 11 from shaft couplers 12 and 16, and removing the cap 54 ofthe center bearing block 13 by means of the bolts 44.

A magnetic printing cylinder 15, which in the instant case, is similarlyproportioned to the photoscanned cylinder 10, but not necessarily so,has an axial shaft 45. The said magnetic printing cylinder 15 issupported by means of the axial shaft 45 which has one extremityconnected to said coupler 16, and the other rotatably supported in asplit bearing of an end-bearing block 17 having a removable cap 13attached by a pair of bolts 19.

It thus appears that the magnetic printing cylinder 15 is also rotatablymounted and easily removed by disconnecting the axial shaft 45 from thecoupler 16 and removing the cap 18 of the bearing block 17 by means ofthe bolts 19. The coupler 16, joining the ends of the axial shafts 11and 45, serves to synchronize the rotational motion of the photoscannedcylinder 10 and the magnetic printing cylinder 15.

The magnetic printing cylinder 15 is a body having a peripheral surfacearea of good magnetic quality. This may be very satisfactorily achievedby using the newly developed plating process disclosed in the U.S.Patent application of Douglas C. Wendell, Jr., and Theodore H. Bonn,entitled Electrodeposition of a Magnetic Coating, filed on January 5,1950 under Serial No. 137,028, new Patent No. 2,644,787 granted July 3,1953, providing for nickel-cobalt plating resulting in a surface havinghighly desirable magnetic properties, for instance, a coercivity of over800 oersteds and a remanence of 10,000 gauss.

A conventional optical-electric transducer 20 comprising a photocell100, a light source and a focussing lens, is adapted to readrepresentations appearing upon the peripheral intelligence-bearingsurfaces of the photoscanned cylinder lli by successively sensing smallareas, in a process of scanning. Proper operation may be effected whenthe optical-electric transducer 20 is designed to rest upon the surfaceof the photoscan cylinder 10 or assume a position slightly above saidsurface. The scanning mechanism to which said optical-electrictransducer 20 is attached will be described in detail later.

The optical-electric transducer 20 has a terminal 21 which may beconnected to the input of an electronic signal transforming circuit(FIGURES 4, 5, and 6) which has its output connected to the receptacle25 of a recording head 24.

The said recording head 24 is illustrated in greater detail in FIGURE 2,where it is shown in its operating position, resting upon themagnetizable surface of the magnetic printing cylinder 15. Graphite maybe used to reduce friction between the recording head 24 and the surfaceof the magnetic printing cylinder 15, when said cylinder is rotated.Proper operation may also be effected by positioning the said recordinghead 24 slightly above the surface of said magnetic printing cylinder15.

The recording head 24 comprises a laminated core 51 made of materialhaving a high permeability consisting of two horseshoe-shaped segmentswith two of their ends abutting and the other ends spaced to form a highreluctance gap 53 located adjacent to the magnetizable surface of themagnetic printing cylinder 15. The said laminated core 51 may beimbedded in an insulating material 50 as is the energizing coil 52 whichis Wound about a segment of the laminated core 51 and brought to asignal input terminal 25.

When the coil 52 is energized, a magnetic flux is caused to appear inthe high permeability path of the laminated core 51. Because of the highreluctance gap 53 formed by said laminated core 51, the magnetic fluxtakes a path through the magnetizable surface of the magnetic printingcylinder 15, causing a magnetizing effect thereat related to the signalinput to the energizing coil 52. In this manner, the recording head 24is used to selectively magnetize small surface areas, and by combinationwith a" scanning mechanism described later, may be caused to cover thesurface of said magnetic printing cylinder 15 with a plurality ofmagnetically polarized areas corresponding to the intelligence borne bythe photoscanned cylinder 10.

The recording head 24 may be used as shown, with the gap 53 in thedirection of the relative motion between said head 24 and the magneticprinting cylinder 15, or with. the gap oriented across or transverselyof the direction of the said relative motion, the latter arrangementeliminating the need for certain auxiliary operations when solid blackareas are being recorded.

FIGURE 3 illustrates in section an electromagnetic recording head 60which may be used in place of the electromagnetic recording head 24shown in FIGURE 2. This electromagnetic recording head 60 is comprisedof a stylus-like member 61 having its nonpointed extremity connected toa head plate 62 which joins an extension arm 26; and an energizing coil63 wound about said stylus 61 and returned to a signal input receptacle64. Said energizing coil 63 and most of stylus 61 may be imbedded in aninsulating material 65 which is shown in cross section.

The electromagnetic recording head 60 operates with the pointed end ofits stylus 61 contacting the magnetizable surface of a magnetic printingcylinder 66. The friction resulting upon the motion of said magneticprint ing cylinder 66 may be reduced to a minimum by using a suitablelubricant. Effective operation of the electromagnetic recording head 60may also be accomplished by positioning the pointed end of the stylus 61slightly above the surface of said cylinder 66.

The magnetic printing cylinder 66 which is used in combination with theelectromagnetic recording head 60 differs from the magnetic printingcylinder 15 in that it is desirable that the core material of themagnetic printing cylinder 66 be characterized by a reasonably low valueof coercivity and a high value of remanence. This is so because the bodyof the cylinder 66 is directly in the path of the magnetic fluxdeveloped by the energizing coil 63 of the electromagnetic recordinghead 60. The magnetic flux flows through the stylus 61 to enter the bodyof the magnetic printing cylinder 66 in a path substantiallyperpendicular to its surface, then passes through the axial shaft 45 toother magnetic flux conducting bodies, until it enters the extension arm26 whence the magnetic circuit is completed by returning through thehead plate 62 to said stylus 61. A shortened flux path may be achievedby directly returning flux entering the magnetic printing cylinder 66through the stylus 61, by extending a flux conducting member from theelectromagnetic recording head 66 contacting the printing cylinder overan extended area (thereby reducing flux density) not greatly removedfrom said stylus 61. In this manner, magnetic flux perpendicularlyentering the surface of the magnetic printing cylinder 66 effects aresult similar to that accomplished by the electromagnetic recordinghead 24 which utilizes a flux tangential to the surface of the magneticprinting cylinder 15, the elemental magnetic structures being normal tothe surface in one case and longitudinal in the other. Although theelectromagnetic recording head 24 is considered desirable, use of theelectromagnetic recording head 60 may be advantageous in certain cases.For example, when head 60 is utilized, the signal scanning unit ofFIGURE 1 may be used in association with a simplified electronic signaltransforming circuit which need not contain a recording signaloscillator to effect recordation. This will be explained in greaterdetail below in connection with the discussion of the electronic signaltransforming circuit shown in FIGURE 4.

Referring once more to FIGURE 1 for a description of the scanningmechanism of the signal scanning unit, the optical-electric transducer20 is joined to a traversing block support 23 by means of a flexiblespringlike extension arm 22 which causes said optical-electrictransducer 20 to remain in contact with the surface of said photoscannedcylinder 10. In a like manner, the electromagnetic recording head '24 isconnected to another traversing block support 2 7 by means of anextension arm 26, maintaining said electromagnetic recording head 24 incontact with the surface of the magnetic printing cylinder 15.

The traversing block supports 23 and 27 are equally proportioned and arepositioned parallel to each other by threadedly engaging a pair ofparallel feeding rods 30 and 31. Each of the said feed rods 30 and 31has a right hand thread along one-half of its length and a left handthread along the remaining half of its length, so that when both feedrods 30 and 31 are caused to rotate in the same direction, saidtraversing block supports 23 and 27 will either move in a directiontowards each other or away from each other. The motion of the traversingblock supports 23 and 27 is controlled by a guide rod 32 which passesthrough openings in said block supports 23 and 27 in a directionparallel to said feed rods 30 and 31 to prevent possible jamming of thescanning mechanism.

The parallel feed rods 30 and 31 and the guide rod 32, which support thetraversing block supports 23 and 27, are in turn supported by means ofsaid end-bearing blocks 14 and 17 which receive the ends of said guiderod 32 and rotatably mount the ends of said feeding rods 30 and 31.

The end-bearing blocks 14 and 17 are each anchored to a base plate 40 bymeans of a set of four fastening bolts 42 and 43, respectively. Adriving motor 35 is also mounted upon said base plate 40 by bolts 41 andhas its shaft 28 joined by means of a motor shaft coupler 34 to thedrive shaft 33. The drive shaft 33 has a drive gear 36 keyed to rotatewith it. The two ends of the feeding rods 30 and 31 which protrudethrough the endbearing block 14, each has a driven gear 37 and 38,respectively, keyed thereto. The drive gear 36 directly engages thedriven gear 37; and an idler wheel 38 is positioned between the drivengears 37 and 39 to mesh with each.

To effectuate scanning in the signal scanning unit, the driving motor 35is energized; its rotational motion is transmitted to the photoscannedcylinder 10 and the magnetic printing cylinder 15, which are coupledtogether by means of the synchronizing coupler 16. Simultaneously,motion is conveyed by means of the drive gear 36 to the driven gears 37and 39, which are coordinated and caused to revolrve in the samedirection by means of the idler wheel 38. When the feed rods 30 and 31rotate, the resulting motion of the traversing block supports 23 and 27,moving toward or away from each other, causes the optical-electrictransducer 20 and the electronic recording head 24 to traverse thelengths of their respective cylinders 10 and 15 in opposite directions,While said cylinders 10 and 15 revolve under them. In this manner, boththe photoscanned cylinder 10 and the magnetic printing cylinder 15 arecorrespondingly scanned by the optical-electric transducer 20 and theelectromagnetic recording head 24, respectively.

It should be noted that the scanning path can be changed to increase ordecrease the fineness of scan by varying the ratio of the diameters ofdrive gear 36 to driven gear 37 or 39, and, to some extent, by varyingthe thread pitch of the feed rods 30 and 31.

It should also be obvious to those skilled in the art, that this signalscanning unit may easily be adapted to scan the cylinders 10 and 15,each at a different rate, and that each cylinder need not revolve at thesame speed, nor be equally proportioned.

For example, the cylinders 10 and 15 may be scanned at different ratesby appropriately varying the pitch of the threaded portions respectivelyassociated with the blocks 23 and 27 of the rods 30 and 31, Furthermore,

the rate of angular rotation of the cylinders 10 and may be varied withrespect to each other by substituting for the direct coupling unit 16 aconventional angular rotation converting unit such as a gear reductionchain between the cylinders 10 and 15. Likewise, the diameter of thecylinder 10 may be larger or smaller than the diameter of the cylinder15. Such modifications are obvious to those skilled in the art.

The cylinders 10 and 15, in the instant case, are scanned in oppositedirections so that the configuration produced upon the magnetic printingcylinder 15 will be a mirror image of the scanned representation uponthe photoscanned cylinder 10. This is done for the purpose of achievinga printed representation which reproduces the original scanned oncylinder 10. This will be apparent from FIGURE 10, whichdiagrammatically shows the magnetic printing unit including the magneticprinting cylinder 15.

The signal scanning unit may be advantageously supplied With limitswitches to turn 011? the driving motor 25 when the traversing blocksupports 23 and 27 have reached their end positions in scanning process.

It is estimated that a scanning speed of 100,000 spots per second isfeasible with the signal scanning and transfer unit here described,whereas speeds from 5,000 to 10,000 spots per second measure theoperating limitations, of present day purely optical facsimile devices.

FIGURE 4 illustrates schematically an electronic signal transformingcircuit used in association with the signal scanning and transfer unitof FIGURE 1 and includes the photocell 100 of the optical-electrictransducer as well as the laminated core 51 and the energizing coil 52of the recording head '24. The recording head 60 may be used in place of24, in FIGURES 4, 5, or 6.

The photocell 100 has its cathode connected directly to a potential ofzero volts at a terminal 104, and its anode connected through seriesresistors 101 and 102 to a suitable positive potential at a terminal103. A filtering capacitor 105 is connected in parallel with said seriesconnected photocell 100 and resistor 101. The anode of said photocell100 is also coupled by means of a capacitor 106 to the signal input grid107 of the photocell coupling valve 109; said signal input grid 107being returned to zero potential at terminal 104 by means of a gridresistor 108. The photocell coupling valve 109 has its cathode 110returned to a Zero potential at terminal 104 by means of a cathoderesistor 111, its screen grid 114 returned to the positive potentialterminal 103 through a resistor 115 and linked to the zero potentialterminal 104 through a bypass capacitor 116, its anode 112 returned tothe positive potential terminal 103 through the anode resistor 113 andcoupled to the control grid 118 of a split load amplifier valve 119 bymeans of the coupling capacitor 117.

In operation, the photocell 100, which is light-sensitive, receiveslight impulses from the object being scanned on the photoscannedcylinder 10 and responds by changing its conductivity. The light sourcemay be incorporated in the head 20, using any conventionalconfiguration. Upon receipt of a light impulse the voltage drop acrossthe photocell 100 decreases causing the transmittal of a negativevoltage impulse to the signal input grid 107 of the photocell couplingvalve 109. Said negative impulse results in a positive amplified signalbeing placed upon the control grid 118 of the split load amplifier valve119.

The said split load amplifier valve 119 has its control grid 118 and itscathode 121 respectively returned, by means of a grid resistor 120 and acathode resistor 122, through a series load resistor 123 to the zeropotential terminal 104. The said cathode 121 is connected to controlgrid 129 of a t-riode 131 in a flip-flop circuit by means of a couplingcapacitor 127; the anode 124 is likewise connected to the control grid128 of the remaining triode 130 of said flip-flop circuit by means ofthe coupling capacitor 126. Said anode 124 receives a positive potentialthrough an anode load resistor joined to the positive potential terminal103..

The triodes and 131 of said flip-fl0p circuit have their anodes 139 and140 respectively connected, by means of anode resistors 141 and 142, tosaid positive potential terminal 103, and each is respectivelycrossconneoted to the control grids 129 and 128 by means of associatedparallel resistor-capacitor combinations 136 and 135. The cathodes 137and 138 are directly linked to the zero potential terminal 104; thecontrol grids 128 and 129 are supplied with negative bias by beingreturned respectively through grid resistors 132 and 133 to a negativepotential terminal 134. The control grid 128 is joined to the terminal144 and the control grid 1'29 is joined to the terminal 145 of areversing switch 143 which has its selecting arm coupled by means of theresistor 146 to the second control electrode 147 of a signal gatingvalve 148.

When a positive signal voltage appears upon the con trol grid 110 of thesplit load amplifier valve 119, the increased current fiow therethroughcauses the cathode 121 to become more positive and the anode 124 tobecome more negative. The positive-going pulse on the cathode 121 istransmitted to the control grid 129 to cause the valve 131 to becomeconductive, while the negative-going impulse upon anode 124 istransmitted to the control grid 128 of valve 130 to cause this triode tobecome nonconductive. This state of the flip-flop circuit is maintaineduntil a positive impulse is delivered to the control grid 128 and anegative impulse is delivered to the control grid 129, as when thecontrol grid 118 receives a negative-going impulse from the photocellcoupling valve 109. The reversing switch 143 serves to select the sourceof the signal appearing upon the second control grid of the gating valve148.

The first control electrode of said gating valve 148 is coupled to a tapon an oscillator coil 162 in an oscillator circuit, isolated by means ofa shield 172, through a resistor 156 and a signal output switch 153contacting terminal 159 in series with a coupling capacitor 161. Theoscillator coil 162 connected in parallel with a tuning capacitor 163,has a tap near one end directly connected to the zero potential terminal104, and its other end coupled by means of a capacitor 164 to the anode166 of an oscillator valve 165. The cathode 167 of said oscillator valveis directly linked to the zero potential terminal 104, the anode 166being returned to the positive potential terminal 103, by means of ananode inductor 168. The control grid 170 is connected to feedback coil169 through a parallel resistor-capacitor combination 171.

The gating valve 148 has its first control electrode 155 returned to thezero potential terminal 104 through the series connected resistors 156and 157, its cathode 149 directly returned to the zero potentialterminal 104, its screen electrode 152 returned to the positivepotential terminal 103 through a resistor 153 and returned to the Zeropotential terminal 104, it screen electrode 152 returned to the positivepotential terminal 103 through a resistor 153 and returned to the zeropotential terminal 104 by means of a by-pass capacitor 154, and itsanode 150 returned to the positive potential terminal 103 through ananode resistor 151 and connected to the control grid 174 of a poweroutput valve 175 by coupling capacitor 173.

Signals are not passed by the signal gating valve unless a positivegating signal is present upon the second control electrode 147. When apositive gating signal appears upon the second control electrode 147 ofthe signal gating valve 148, and the oscillator signal output switch 158is contacting terminal 159, the oscillatory signals generated in thesaid oscillator circuit are passed through the gating valve 148 toappear upon the control electrode 174 of the said power valve 175. Ifthe oscillator output switch 158 is in the off position, contactingterminal 160, a single impulse of duration controlled by the Varioustime constants, is transmitted each time said gating valve 148 becomesconductive or nonconductive due, respectively, to the appearance of apositive or negative signal upon the second control electrode 147.

The control electrode 174 of the said power output valve 175 is returnedto the zero potential terminal 104 through a grid resistor 176; thecathode 177 is likewise returned through a cathode resistor 178; thescreen grid 17) is maintained at a positive potential by connectionthrough a resistor 180 to the positive potential terminal 103 and to thezero potential terminal 104 by means of a bypass capacitor 181. Theanode 182 is connected to the positive potential terminal 103 throughthe primary coil 184 of a signal output transformer 183, which has itssecondary winding 185 connected to the head coil 52.

Signals passed by the signal gating valve 148 appear upon the controlelectrode 174 of the power output valve 175. These signals are amplifiedand delivered to the signal output transformer 183 and thence to thehead coil 52 for purposes of magnetic recording as previously related.

The reversing switch 143 is useful when it is desired to make eitherpositive or negative reproductions of the intelligence being scanned.This is so because a positive potential will appear upon terminal 144when a negative potential appears upon terminal 145, and a negativepotential will appear upon terminal 144 when a positive potentialappears upon terminal 145. Thus, by selecting the proper terminal 144,or 145, a positive or negative reproduction, respectively, may beachieved.

At the same time, it may be desirable to modify the scanner drivearrangements, so that when a positive is to be produced from a positive,or a negative from a negative, the scanning heads move in the samedirection, rather than in opposing directions as shown in theillustrative arrangement of FIGURE 1, which latter is suited for theproduction of positives from negatives, or the production of negativesfrom positives. Obvious mechanical structural modifications will suificefor this purpose. If desired, these modifications may be accomplished bysimple, lever actuated changeover mechanisms, alternatively engaging oneor another of reversely threaded feed drives, and this, in turn, may beinterlocked with the action of switch 143.

The oscillator circuit including valve 165 is useful when material whichhas not been previously screened is being scanned by the photocell 100.This is so because, when a dark area is being scanned for positivemagnetic recordation, a magnetic pole will be created when scanningpasses from a white area to a black area, with the second pole appearingwhen passing from the black area to a white area. In the reproductionprocess, paramagnetic particles are used, which are attracted todifferent degrees to the surface of the magnetized drum. Since suchparticles are attracted mos-t strongly in the regions of maximumgradient, they would cluster only at the two poles. Thus, only theoutlines of the dark area would be defined by the particles soattracted. By recording impulses derived from said oscillator when blackareas are scanned, magnetically attractable particles can be evenlydistributed over a magnetized recording area corresponding to a blackscanned area, by virtue of the numerous pole pairs generated. 1

The utility of the electronic signal transforming circuit shown inFIGURE 4 is limited to high contrast representations, such ascharacterizations represented in black and white. The contrast must alsobe suflicient, so that, when passing from a dark to a light area or froma light to a dark area, a sufficient impulse is transmitted to triggerthe flip-flop circuit comprised of valves 128 and 131 from one of itstwo states to its other state. The circuit elements may be adjusted sothat said circuit will be sensitive to a given change in light intensityreceived by the photocell 100. Other electronic signal transformingcircuits will hereinafter be discussed which are capable of recordingnot only black and White contrast, but intermediate contrasting shades.

In this connection, the use of recording head 60 in place of recordinghead 25 is of interest, for this permits the elimination of theoscillator, signal gating circuit and controlling flip-flop withoutsubstantial impairment of the systems ability to reproduce extendedblack areas. As has already been pointed out, the paramagnetic particlesare attracted to the magnetic poles. With the magnetizing field normalto the cylinder surface, only the poles are exposed, so that it becomesunnecessary to periodically interrupt the head-exciting current toinsure the presence of the attracting magnetic gradients. Likewise, thepole strength is susceptible to graduated variation, so thatcontinuously varying contrast ranges may be achieved in the absence ofthe oscillator, signal gating circuit and controlling flip-flop, Withinthe limits of the time constants of the associated circuit elements.

An electronic signal transforming circuit, which is also useful inassociation with the signal scanning unit of FIG- URE 1, is shown inFIGURE 5. The anode of the photocell connects through a series resistor205 to the junction point of voltage dividing resistors 210 and 209,respectively, connecting to a positive potential source and a zerovoltage potential source. The anode of said photocell 100 is alsoconnected with the cathode 201 through a small capacitor 206 which maycomprise distributed capacity; the photocell cathode is connected inseries with a resistor 203 to the contact arm of a potentiometer 204,which connects between zero voltage potential and a negative voltagepotential. The photocell coupling valve 200 has its control electrode202 directly connected to the cathode of photocell 100, its cathode 201directly joined to a potential of zero volts, its screen grid 207connected to the junction point of voltage dividing resistors 210 and209 and bypassed to the cathode 201 by capacitor 208, and its anode 299returned to a positive potential through the anode resistor 211.

A threshold control valve 212 has its cathode 214 directly linked to theanode 299 of said photocell coupling valve 200, and its anode 213connected to the control electrode 220 of a reactance valve 217 andthrough an anode resistor 215 to a tap on a potentiometer 216, which isconnected from a zero voltage potential to a positive voltage potential.

The photocell 100 becomes more conductive with increasing lightintensity. The more conductive the photocell 100 is, the less positivebecomes the potential on the control grid 202 of the photocell couplingvalve 200; the less conductive the photocell 100 becomes, the more posi-.tive is the voltage upon the control grid 202. The potentiometer 204may be adjusted to bias the control grid 202, so that the signal outputfrom the photocell coupling valve 200 is proportional to the lightintensity sensed by the photocell 100. The voltage appearing upon theanode 299 of the photocell coupling valve 200 swings negatively as thelight intensity received by the photocell 100 decreases.

The threshold signal which will be passed by the threshold control valve212 can be adjusted by means of the potentiometer 216, which determinesthe positive voltage upon the anode 213 of said threshold control valve212. Thus, signals will only be passed when the cathode 214 is morenegative than the anode 213, which means that light intensity sensed bythe photocell 100 must be less than a given value before the signalcontrol electrode 220 of the reactance valve 217 will be affected.

The reactance valve 217 has its screen electrode 226 returned to apositive voltage potential through a resistor 227 and linked to thecathode 223 by means of a by-pass capactior 228; its suppressor grid 222is directly joined to the cathode 223, which is returned to zeropotential by means of parallel resistor 224 and capacitor 225; its anode218 is connected by means of a resistor 219 to the said controlelectrode 221), which is returned to ground by means of a phase-shiftingcapacitor 221. The anode 218 of said reactance valve 217 is joined'toa'positive voltage potential by being connected to the upper half 229 ofan oscillator coil, which has its center tap connected to a positivepotential and by-passed by a capacitor 238 to a zero potential source.The anode end of the oscillator coil 229 is linked to the controlelectrode 233 of a variable frequency oscillator valve 232 by means ofseries coupling capacitors 230 and 231. The junction point of couplingcapacitors 230 and 231 is connected to the ground bus by a fixed tuningcapacitor 236 connected in parallel With the variable tuning capacitor237. The control electrode 233 of said variable frequency oscillatorvalve 232 is returned to its cathode 240 by means of series connectedresistors 234 and 250; the cathode 246 is directly linked to zeropotential; and the anode 239 is excited from a positive potentialthrough the lower half 235 of said center-tapped oscillator coil, and isconnected to the second signal control electrode 243 of asignal-converting valve 242 by means of a coupling capacitor 241.

The reactance valve 217 is effectively connected across one-half of theoscillator coil 229, having a given reactive effect determinative of thesignal frequency generated by the variable frequency oscillator valve232. The variable tuning capacitor 237 may be used to determine thefrequency of oscillation when the reactance valve 217 receives no signalfrom the photocell 100. When the threshold control valve 212 passessignals to the control electrode 220 of the reactance tube 217, thereactance acrossit-he half of the oscillator coil 229 is caused to varythereby changing the frequency generated by the variable frequencygenerator. The change in the frequency generated is dependent upon thechange in voltage at the control electrode 220 of the reactance tube.

The said signal converting valve 242 has its first signal controlelectrode 245 connected by means of a coupling capacitor 247 to a beatfrequency oscillator identical with the variable frequency oscillatorjust described, with the exception that it is not associated with areactance valve. The said beat frequency oscillator is isolatedelectrically by means of a shield 259 which is connected to zeropotential.

The output signal from the beat frequency oscillator is in partdelivered to said variable frequency oscillator by means of asynchronizing control valve 260, which'has its control electrode 261connected to the coupling capacitor 24], its cathode 262 returned tozero potential by means of a cathode resistor 263, its screen electrode264 connected through a resistor 265 to a positive potential voltage andthrough a parallel resistor and capacitor combination 26-to a zeropotential source; its anode 267 is returned to a positive potentialsource through an anode resistor 26% and is connected to the junctionpoint of grid resistors 234 and 250, by means of a variable couplingcapacitor 258.

The function of the synchronizing control valve 260 is to introduce intothe variable frequency oscillator a sig nal generated in the beatfrequency oscillator for the purpose of locking said variable frequencyoscillator with the beat frequency oscillator, when the naturalgenerated frequencies of said oscillators do not differ greatly. Thenatural frequency difference beyond which the oscillators will not lockin, is determined by the amount of lock-in signal delivered to thevariable frequency oscillator, which amount can be adjusted by thevariable coupling capacitor 258. The said synchronizing circuit isuseful for the reason that it is desirable to have the variablefrequency osci lator track with the beat frequency oscillator when thereactance valve 217 is not activated by the photocell 100. Itsusefulness is evident although the frequency of the variable frequencyoscillator may be manually adjusted by means of the variable tuningcapacitor 237, because its operation isto -produce an effect which issubstantially the equivalent of constantly adjusting said capacitor 237for the smallest deviations in the oscillator frequencies caused-byslight and irregular changes in the oscillator components over a timeperiod. The said synchronizing control circuit, also acts like athreshold control, because of the adjustability of the difference inoscillator frequencies necessary before said oscillators Will not lockin any longer; this is an effect which is additive to that of saidthreshold control circuits associated with Valve 212.

The first control electrode 245 and the second control electrode 243 ofsaid signal converting valve 242 are each negatively biased by beingrespectively returned by grid resistors 246 and 244 to a negativevoltage potential; the cathode 269 is directly returned to a potentialof zero volts; the screen electrode 27f) is returned to a positivevoltage potential through a resistor 271; and the suppressor electrode272 is returned to a positive voltage potential by means of aresistor-capacitor combination 237 connected in series with saidresistor 271. The suppressor electrode 272 is linked by means of aby-pass capacitor 274 to the anode 275, which is returned to a positivepotential by means of an anode resistor 276. The said anode 275 is alsocoupled to the control electrode 280 of a signal amplifier valve 281 bymeans of a coupling capacitor 277.

The signal converting valve 242 receives signals generated by thereference frequency oscillator on its first signal electrode 245 andsignals generated by the variable frequency oscillator on its secondsignal electrode 243, which results in a signal output appearing as avoltage drop across the anode resistor 276 equal to the difference inthe frequencies appearing upon said first and second signal controlelectrodes 245 and 243. This is so because the frequencies equal to thesum of the signal frequencies appearing on the first and second signalcontrol electrodes 245 and 243, and frequencies equal to the signalfrequencies appearing upon said electrodes are by-passed by means of thecapacitor 274 and the capacitance of combination 237, as well as thedistributed capacitance of the signal converting valve 242. Thus theonly time that a signal will appear across the anode resistor 276 iswhen the frequencies appearing upon the first and second controlelectrodes 245 and 243 are not the same; and the frequency of saidsignal output is equal to the difference between the frequencies uponthe said first and second signal control electrodes 245 and 243.

The control grid 280 of signal amplifier valve 281 is returned to zeropotential through a grid resistor 278; the cathode 282 is returned tozero potential through a cathode resistor 283; and the anode 284 isreturned to a positive potential through the anode resistor 285, and iscoupled to the control grid 289 of a power amplifier valve 288 by meansof a coupling capacitor 286.

The said control electrode 289 of the power output valve 288 is returnedto zero potential by means of a grid resistor 287; the screen grid 292is joined to the junction point of two dividing resistors 294 and 293,respectively connecting to a zero potential source and a positivepotential source. The anode 295 of said power output valve 288 isreturned to a positive potential through the primary winding 297 of animpedance matching transformer 296 which has-its secondary winding 298connected to the energizing coil 52 of the electromagnetic recordinghead 24.

The alternating current signal appearing across the anode resistor 276is delivered to the signal control electrode 280 by means of thecoupling capacitor 277, and amplified by the signal amplifier valve 281which drives the power output valve 288. As already described, thesignal output from the power output valve 288 is used to activate theenergizing coil 52 which results in magnetically effecting amagnetically susceptible surface.

lt maynow be noted that for all values of light i-m 13 tensity below agiven determined value, dependent upon the adjustment of the thresholdcontrol rheostat 216 and the synchronizing control capacitor 258, themagnetic recording frequency will be directly proportional to thedarkness of the area being scanned by said photocell 100. Tangentialrecording as efiected by recording head 24 places two magnetic polesupon the magnetic printing cylinder 15 for each recording pulse, thedistance between said poles decreasing with the increase of pulsefrequency resulting in a greater concentration of magnetic poles andincreased density of magnetic particles on the work surface. Whenrecording head 60 is employed for perpendicular magnetic recording afluxfrequency characteristic may be utilized which, with increasingsignal frequency proportionally increases the intensity of flux enteringthe magnetic printing cylinder, or the tuning of the referenceoscillator may be displaced to cause the beat frequency to increase withincreasing light intensity, making use of the natural tendency ofrecording head flux to decrease with increasing frequency. Because thedensity of and the amount of attractable particles attracted by amagnetically polarized surface can thus be made dependent upon therecording frequency, it is possible to print in a plurality of shadesintermediate between black and white by the utilization of the instantelectronic signal transforming circuit. The proper adjustment of thethreshold control depends upon the clarity of the material beingscanned. The threshold control provides for better reproduction byreducing the sensitivity of the circuit as when the scanned material hasan undesirable noise background, as would result from a soiled or dirtybackground. An advantage is also noted in that by use of frequencymodulation, a greater signal to noise ratio is obtained by virtue of theinherent qualities of this circuit.

The electronic signal transforming circuit illustrated in FIGURE 6,which can also be used in association with the signal scanning unit ofFIGURE 1, results in constant frequency magnetic recordationaccomplishing gradations in shade between black and white by varying thework cycle; in other words, changing the size of magnetically polarizedspots upon the magnetically susceptible surface area.

The photocell 100 has its anode returned to a positive voltage potentialthrough the series resistor 300 and its cathode returned to the contactarm of a potentiometer 301, which is connected from a source of zeropotential to a negative potential. A filter capacitor 310 is con nectedfrom said positive voltage source to said source of zero potential. Aphotocell coupling valve 302 has its control electrode 303 directlyconnected to the anode of said photocell 100, its cathode 304 directlyconnected to zero potential, its screen grid 305 connected to thejunction point of two voltage dividing resistors 306 and 307,respectively connected to a positive voltage potential and a zerovoltage potential, and its anode 308 connected by means of an anoderesistor 309 to a positive voltage po tential and directly linked to thecenter tap of the secondary winding 312 of a signal input transformer310.

The conductivity of the photocell 100 being substan tially proportionalto the light intensity sensed by it delivers a negative-going signal tothe control grid 303 of the photocell coupling valve 302 as it becomesmore conductive. This results in a positive-going signal on the anode308, which is delivered to the center tap of the secondary coil 312 ofthe input signal transformer 310. Thereby the positive voltage deliveredto the said center tap is related to the light signal intensity read bythe photocell 100, becoming greater as the light intensity increases.

The primary winding 311 of said signal input transformer 310 has one endconnected to a positive voltage potential and the other joined to theanode 314 of a signal integrating valve 313, which has its cathode 315directly joined to zero potential and its control grid returned to zeropotential through the parallel resistorcapacitor combination 316. Saidcontrol electnode 358 is joined through a resistor 317 connected inseries with a coupling capacitor 318 to the anode 320 of a multivibrator coupling valve 319.

Said multivibrator coupling valve 319 has its cathode 322 directlylinked to zero potential, its anode 320 returned to a positive voltagepotential through an anode resistor 321, and its control electrode 323negatively biased by means of returning a grid resistor 324 to anegative voltage potential.

The control grid 323 of said multivibrator coupling valve 319 is linkedby means of a resistor 325 in series with a coupling capacitor 326 tothe anode 328 of the valve 327 in a multivi-brator circuit, which alsocontains the valve 329. Each Inultivibrator valve 327 and 329 has itsanode 328, 330 returned, respectively, by means of a resistor 331 or 332to a positive voltage potential; the said anodes 328 and 330 are alsocross-connected by related coupling capacitors 333 and 334, to controlelectrodes 336 and 335, respectively. The control electrodes 335 and 336are respectively returned to zero potential through resistors 337 and338; the cathodes 339 and 340 are directly returned to zero potential.

The said multivibrator circuit develops an essentially square Wave of afrequency determined by the capacitive and resistive values of theelements utilized. One of said multivibrator valves, beingnonconductive, becomes conductive to transmit a negative impulse to theother multivibrator valve, causing it to become nonconductive. When thisvalve again becomes conductive, due to the draining 011 of said negativecharge through a grid leak resistor, a negative impulse is passed to cutofr the other conducting multivibrator valve. This sequence is followedat a given rate to generate a square Wave which is delivered to themultivibrator coupling valve 319.

The said multivibrator coupling valve 319 is alternately driven tocutoff and saturation by the signal derived from said multivibratorcircuit. This provides additional sharpening of the square wavedeveloped in the multivibrator circuit. The output of said multivibrator coupling valve 319 is delivered to an integrating circuitcomprised of the resistor 317 and the parallel capacitor resistorcombination 316. By the process of integration, the square wave isconverted to a triangular wave which appears on the control grid 358 ofthe signal integrating valve 313. The said triangular wave is amplifiedby the signal integrating valve 313, and delivered to the input winding311 of the signal input transformer 310. FIG- URE 7 graphicallyrepresents the idealized signal voltage across the input coil 311 :ofsaid signal input transformer 310.

-One end of the secondary winding 312 of the signal input transformer310 is connected through a limiting resistor 341 to the anode 345 of alimiting diode 343 and to the control electrode 351 of a signal outputtriode 349. The other end of said secondary winding 312 is likewiseconnected through a limiting resistor 342 to the anode 346 of a limitingdiode 344 and to the signal electrode 352 of a signal output triode 350.The cathodes 348, 347, 358, 359, respectively, of the valves 344, 343,349, and 350 are all directly returned to zero potential. The anodes 353and 354 of triodes 349 and 350 are each respectively connected to theopposite end of the pri mary winding 356 of the signal outputtransformer 355, which has the center tap on its primary winding 356returned to a positive potential, and its secondary winding 357connected to the energizing coil 52 of the electromagnetic recordinghead 24.

The alternating signal appearing on the primary winding 311 of thesignal input transformer 311 appear across the secondary winding 312,and is delivered degrees out of phase to the anodes 345 and 346,respectively, of the limiting diodes 343 and 344 through limitingresistors 341 and 342, in addition to the signal voltage derived fromthe photocell coupling valve 302. B by-passing positive signals, thelimiting diodes 343 and 344, respectively, prevent positive signals fromappearing on the signal control electrodes 351 and 352 respectively ofsaid signal output triodes 349 and 350. In some cases, limiting may beachieved without the use of said limiting diodes 343 and 344 because ofthe limiting properties of the triodes 349 and 350, due to conduction ofthe signal electrodes 351 and 352, when they become positive. It thusappears that the signal output from the signal out put triodes 349 and350 is restricted by the limited excursion of their respective controlelectrodes 351 and 352 which ranges from zero volts due to the limitingdiodes 343 and 344 to values beyond the cutofi points of the valves 349and 350. The actual excursion of the con trol electrodes 351 and 352,respectively, of the signal output triode 349 and 350 depends upon theamount of clipping of the triangular wave derived through the signalinput transformer 310, which amount is determined by the value ofpositive voltage signal delivered to the tap of the secondary winding312 by the photocell coupling 302. The greater the light intensity of anarea scanned by the photocell 100, the higher will be the positivevoltage delivered by the photocell coupling valve 302 to the center tapwinding 312; this results in greater clipping of the triangular wave, asmaller excursion of the control electrodes 351 and 352, and a signaloutput at the transformer 355, similar to the graphic representationshown FIGURE 8. When the light intensity at the photocell 100 isrelatively low, the voltage delivered by the photocell coupling valve302 is less positive, resulting in less clipping of said triangularwave, giving a signal output at the transformer 305 similar to thegraphic representation shown in FIGURE 9.

The tops and bottoms of the triangular wave represented in FIGURE 9 areflattened because the control electrodes 351 and 352 are, in this case,driven past the cutolf point of the valves 349 and 350 respectively. Ifthe Wave forms of FIGURES 8 and 9 are compared, it may be noted that,although the frequency in both cases is the same, the work cycle andamplitude of the Wave form shown in FIGURE 9 corresponding to thescanning of a dark area by the photocell 100, is greater than that ofthe wave form shown in FIGURE 8, which corresponds to the scanning of anarea of higher light intensity. Thus, by this means, a large gradationof light intensities are presented, not by increasing the frequency ofthe recording cycle, but by increasing the amplitude and recording workcycle of the magnetic recording signal.

Although the three electronic signal transforming circuits justdescribed have all utilized photocells to derive signals of lightintensity from a scanned body, it may be seen that signals may bederived from many other sources for recordation upon a magnetic printingcylinder utilizing the recording portion of the signal scanning unitshown in FIGURE 1. If necessary, synchronization between the recordingsignal and the driving motor may also be utilized, and might be obtainedby use of a synchronizing signal occurring with the recording signal.

The magnetic printing unit illustrated by a diagrammatic view, partiallyin section, shown in FIGURE 10 is adapted to continuously print on amoving print-receiving strip by utilizing the magnetic printing cylinderdescribed earlier which is coupled to a driving motor 450, and hasperipheral areas of selected magnetic polarization obtainable bytreatment in the signal scanning unit of FIGURE 1 used in conjunctionwith an electronic signal transforming circuit, shown in FIGURES 4, 5,or 6.

The said magnetic printer unit contains a particle distributingmechanism 400 which may be secured by means of bolts 462 to a shelf 463which is supported by a vertical back panel 464. A supporting bracket.465 which is also fixedto the shelf 460 beats a journal 466 at itsupper end. Journal 466 receives one end of the axial shaft 45 ofprinting cylinder 15 providing a rotatable mounting. A second supportingbracket which may be identical to bracket 465 and also fixed to shelf460 may be utilized to rotatably support cylinder 15 by retaining theother end of its shaft 45.

A motor 450 may also be supported upon the shelf 463 and arranged todrive the printing cylinder 15 by means of a coupling belt 451 whichpasses around a pulley wheel 452 attached to the shaft of the motor 450and around a pulley wheel 453 fixed to the shaft 45 of cylinder 15.

The particle-distributing mechanism 400 has a suspension chamber 401 anda reservoir chamber 402 formed by a partitioning member 403 whichprovides a pressure safety gap 404 joining said chambers. The magneticprinting cylinder 15 is rotatably mounted upon its axis 45 so that aportion of its peripheral surface partially encloses said suspensionchamber 401. A felt strip 405 which contacts the peripheral surface ofsaid magnetic printing cylinder 15 provides an air seal; and saidmagnetic printing cylinder 15 is positioned to provide an air intake gap406 at another place along its periphery. A baflling structure 407within the suspension chamber 401 is positioned to form a circulatingfluid path providing a tangential path along a portion of the peripheralsurface of the magnetic printing cylinder 15 which forms an insidesurface of the suspension chamber 401. A blower 411, connected to ablower motor 412, is located in the fluid circulating path within thesuspension 401, so that its intake adjoins a low pressure side 409 andits outlet is adjoined to the high pressure side 408 of said suspensionchamber 401. Two inspection windows 417 (one of which is shown) arelocated across from each other in the vertical walls of the suspensionchamber 401 on the high pressure side 408.

The lower portion of said reservoir chamber 402 contains apowder-feeding worm 414 which is helically ridged and has its endportion extending through a feeding orifice 415 into the high pressureside 408 of said suspension chamber 401. Said powder-feeding worm 414,which is rotatably mounted, has its other end connected to afeed-driving motor 416. The upper portion 418 of said reservoir 402 isprovided with an air vent 419 enclosed by a screen 420.

For operating purposes the reservoir chamber 402 at its bottom portionis supplied with a powder 413 which contains magnetically attractableparticles which are delivered into the high pressure side 408 of thesuspension chamber 401 by the rotating motion of the powder-feeding worm414 activated by the feed-driving motor 416. The magneticallyattractable particles may be made of a paramagnetic material such asiron which has been powdered. The blower motor 412 actuates the blower411 to cause the building up of a high pressure at the blower output anda low pressure at the blower intake resulting in a fluid circulation asindicated by arrows in FIGURE 10.

Powder particles 421 deposited in the high pressure side 408 of thesuspension chamber 401 are suspended in the air circulated by the blower411 and traverse the fluid circulating path. The suspended particlespassing through the tangential fluid path 410 are attracted tomagnetically polarized areas of the magnetic printing cylinder 15 whichis rotated by the driving motor 450 coupled to the axial shaft 45, thusallowing the sequential distribution of powder particles over the entireperipheral surface of said magnetic printing cylinder 15. The pressuresafety gap 404 and the air vent 419 prevent the build-up of dangerouslyhigh pressures in the high pressure side 408 of the suspension chamber401, by allowing a fluid escape path out of said chamber. The air ventscreen 42-0 besides preventing the entry of outside impurities into thereservoir chamber, separates the suspended powder particles from thefluid escaping through the air mam i7 vent 419, causing such powderparticles to settle to the bottom of the reservoir chamber 419 forre-use by the feeding mechanism.

Air which is lost through the air vent 419 is replaced on the lowpressure intake side 409 of the suspension chamber 401 by incoming airpassing through the air intake gap 406. The air passing through the airintake gap 406 tangential to the peripheral surface of said magneticprinting cylinder 15 and in a direction opposite to the motion of saidsurface to which the suspended powder particles have been attracted,also serves the purpose of removing excess powder particles and cleaningsurface areas not magnetically polarized;

The inspection windows 417 in the side walls of the suspension chamber401 are adapted to cooperate with a fluid opacity measuring device usedoutside said suspension chamber 401. One such fluid opacity measuringdevice which is well known consists of a light source placed at onewindow 417 and a photoelectric cell placed at the other inspectionwindow 417, so that the intensity of light received by the photoelectriccell is substantially proportional to the density of suspended powderparticles in the circulating fluid found in the suspension chamber 401.When the fluid density falls below a given value said fluid densitymeasuring device activates the feed-driving motor 416 causing thedelivery of powder particles to the suspension chamber 401, raising thefluid density to a point where the said fluid density measuring devicedeactivates the feed-driving motor 416. By this method the density ofsuspended particles is maintained at values most satisfactory to theoperation of the particle-distributing mechanism 400.

Reference to FIGURE 11 reveals the circuit of a fluid opacity responsivecontrol device which may be used. A source of light, which may be anincandescent bulb 500, is positionedoutside the device 400 in line withthe inspection Windows 417 of this device. A photoelectric cell 501 ispositioned on the other side of the device 400 in line with theinspection windows 417 and adapted to receive light from theincandescent bulb 500, which passes through both inspection windows 417.It is obvious that the intensity of light from the source 500 fallingupon the cathode of the photoelectric cell 501 is inversely related tothe opacity of the fluid particles suspension contained within thechamber 401 of the device 400.

The anode of the photoelectric cell 501 is returned to positive voltagebus 50 while the cathode is returned to ground potential through avoltage divider 502. The adjustable arm of the voltage divider is linkedto the control electrode of a relay actuating valve 503. Valve 503 hasits cathode returned through a cathode resistor 504 to positivepotential bus and its anode returned to positive potential bus 100through the energizing coil of a motor control relay 505. The movablecontact arm of the motor control relay 505 is in a position contactingits left contact member when not energized. This movable contact arm,however, when actuated by its associated energizing coil contacts itsright contacting member which is joined to a terminal 506. The terminals506 and 507 are connected to an alternating current source of power. Theterminal 507 is returned to ground potential.

The movable contact arm of motor control relay 505 is directly connectedto a first winding 508 of the motor 416. The other end of winding 508 isreturned to ground potential. A second winding 509 of the induction typemotor 416 also has one end coupled to the movable contact arm of relay505 through a phase shifting capacitor 510, while its other end isreturned to ground potential.

In operation, when the fluid suspension in chamber 401 of the device 400is sufliciently opaque, the low intensity of light arriving from thelight source 500 upon the emitting cathode surface of photoelectric cell501 makes the cell 501 only poorly conductive. The control voltagedelivered to the valve 503 at this time is such that 18 a it is alsomaintained at a reduced conductivity. The reduced current flow throughthe energizing coil of relay 505 does not actuate relay contacts.

As the intensity of the light arriving upon the photoelectric cell 501increases with reduction of particle density in the chamber 401, thevoltage upon the control electrode of the valve 503 also increases,rendering it more conductive. When anode current is sufiicientlyincreased through valve 503 and the energizing coil of relay 505, themovable contact arm of relay 505 is actuated to contact its right handcontacting member. This allows the delivery of mains power to thewindings 508 and 509 of motor 416. The actuation of motor 416 causesdelivery of additional particles to the chamber 401 increasing theopacity of the fluid therein. The continued operation of the motor 416reduces the conductivity of photoelectric cell 501 and the controlvoltage delivered to valve 503. When the current delivered to theenergizing coil of relay 505 has been sufliciently decreased, themovable contact arm returns to its deactivated position and cuts offpower supply to the motor 416.

Thus, the upper and lower limits of the range within which the fluidopacity may vary are respectively determined by the drop-out current andthe pull-in current of the energizing coil of motor control relay 505.Variations in the positions of the contact arm of the voltage divider502 allow adjustment of the lower limit of fluid opacity by energizingthe motor 416 when this limit is reached.

Referring again to FIGURE 10, a pressure roller 426 has an axial shaft427, one end of which is rotatably supported in a bearing 470 which ismounted on the vertical back panel 464. The other end of the axial shaft427 of pressure 426 may likewise be supported in a similar bearingmounted in a removable vertical front panel. This removable front panelmay be secured to and held in spaced position with the said back panel464 by means of four spacing brackets 471 which have one end anchored tothe back panel 464 and are adapted to receive a bolt in their otherextremity for fastening the front panel thereto. Thus, when the frontpanel is fixed in position, the pressure roller 426 is rotatably mountedand can be removed by detaching the front panel.

The pressure roller 426 tangentially contacts the peripheral surface ofsaid magnetic printing cylinder 15. The said pressure roller 426 isadapted to receive a printreceiving strip 425 around a portion of itsperipheral surface for the tangential contact of said print-receivingstrip 425 with the powder-bearing surface of said magnetic printingcylinder 15. The pressure roller receives said strip 425 which passesover a guide roller 428 from a strip supply reel 429 which is connectedto a tension motor (not shown). The other end of the print-receivingstrip 425 passing around the pressure roller 426 moves over a guideroller 430 to a strip take-up reel 431 which is connected to atensioning motor (not shown).

A scrub roller 436 has an axial shaft 435 and is also rotatably mountedby having one end of its axial shaft 435 supported by a bearing 472mounted in the back vertical panel 464. The other end of the axial shaft435 may be likewise supported in a bearing carried by the said frontvertical panel.

The scrub roller 436 is rotatably mounted for tangential contact withthe peripheral surface of the magnetic printing cylinder 15 at a placeslightly removed from the said pressure roller 426 along the directionof rotation of said magnetic printing cylinder 15. An electro-magnet 437has its poles in close proximity to a portion of the peripheral surfaceareas of said scrub roller 436. The said scrub roller 436 is connectedto a rotating motor (not shown) which causes the contacting surface ofsaid scrub roller 436 to move in a direction opposite to the directionof motion of the contacted peripheral surface of said magnetic printingcylinder 15.

To effect printing upon the print-receiving strip 425,

19 the surface of the magnetic printing cylinder 15, which has beenexposed to powder particles in the suspension chamber 401, revolves totangentially contact the printing strip 425 backed by the pressureroller 426 which is caused to rotate due to the motion of the magneticprinting cylinder 15. Because of the rotation of the pressure roller426, and because of the pressure which is exerted by it upon themagnetic printing cylinder 15 through the print-receiving strip 425, asatisfactory undistorted transfer of powdered particles to the surfaceof said magnetic printing cylinder 15 is achieved. It may be found desirable to spray the receiving strip 425 with a liquid by means of anatomizer 432 before contact is made with the magnetic printing cylinder15 for the purpose of effecting a more complete transfer of powderedparticles to the printreceiving strip 425.

The scrub roller 436 removes most of the powdered particles from themagnetic printing cylinder which have not been transferred to theprint-receiving strip 425, thereby once more preparing the surface ofsaid magnetic printing cylinder 15 for re-exposure in the suspensionchamber 401 to allow a continuous printing process. The scrub rollerelectro-magnet 437 removes magnetically attractable particles from saidscrub roller 436 allowing its efficient operation. The magnet 437 may bemanually cleaned at intervals, or continuously cleaned by other means.

During the continuous printing operation, the printreceiving strip 425is supplied by the reel 429 which is connected to a tensioning motor(not shown) to impose a given drag opposing the forward motion of saidstrip 425 which is imparted by the motion of the magnetic printingcylinder 15, to provide appropriate tensioning of the print-receivingstrip 425. A tensioning motor (not shown) also powers the strip take-upreel 431 receiving the print-receiving strip 425 coming from thepressure roller 42 6, thereby tensioning the print-receiving strip 425to prevent its slackening.

A strip heater 433 and an electromagnet 434 are positioned adjacent tothe print-receiving strip 425 as it leaves the pressure roller 426, forthe purpose of removing powdered particles, which were transferredearlier from the surface of the magnetic printing cylinder 15 to theprintreceiving strip 425. This removal may be desired when said powderedparticles have been reacted with a reagent sprayed by the atomizer 432upon the print-receiving strip 425 which results in a coloration makingthe further presence of said powdered particles unnecessary and perhapsundesirable. For example, the reagent sprayed by atomizer 432 may bepotassium ferricyan-ide, K Fe(CN) or potassium ferrocyanide, K Fe(CN) ina weak solution of hydrochloric acid (HCl) with a pH of from 2 to 4.When the magnetically attractable particles are powdered iron particles,reaction with the above said reagent produces a blue coloration at thepoint where the iron particle contacts the reagent treated informationreceiving strip 425. The particles may also be sprayed with the reagentafter being received by the strip 425. In either case, the particles maybe removed by magnet 434 after reacting with the reagent.

It is apparent, that the magnetic printing unit shown in FIGURE 10 maybe modified to carry out the various processes described earlier byadding additional atomizers utilizing various spraying liquids andprinting particles or by using a series of magnetic printing units toproduce multicolored prints. Arrangements may further be made for theuse of a liquid as the suspending medium for the particles within thesuspension chamber 401.

The magnetic printing apparatus embodying this invention may be utilizedas a blueprinting machine. In this case, a printing cylinder of thematerial to be reproduced is prepared from the master copy as previouslydescribed utilizing the apparatus shown in FIGURE 1. The apparatus shownin FIGURE 10 is then employed to print as many copies of the originalmaterial as desired.

In addition to all other forms of its utility, the apparatus may beutilized as a block printer to print a series of address blocks on theprint-receiving strip 425. The individual address blocks are thenseparated by cutting and afiixed to the object to be mailed. As amodification of this process, a web of transparent material coated onits outer side with an adhesive composition may be employed in place ofthe strip 425, the adhesive facing the drum 15. The particles are pickedup from the drum by the adhesive surface, to form address blocks, whichare then cut apart and afiixed to the dispatched article by the sameadhesive side. This process is especially valuable because of the easewith which the addresses recorded upon the magnetic printing cylinder 15may be changed.

Refer now to FIGURE 12 which shows apparatus suitable for producingpigmented or dye-coated magnetically attractable powdered particleswhich may be used in the device shown in FIGURE 10. This apparatus maybe comprised of a section of hollow tubing 600 preferably of aninsulating material such as glass. The tubing 600 is formed to providean elbow configuration and has a substantially horizontal section or arm601 and a substantially vertical section or arm 602. The verticalsection 602 of the tubing 600 may be connected with a substantiallyhorizontal section of tubing 603 providing an exhaust tube forcommunicating with the hollow core of the tubing 600. The end of thevertical section 602 of the tubing 600 may be provided with a particlecollecting pan 604.

A conventional fluid exhausting apparatus may be connected to the end ofthe exhaust tube 603 to draw a stream of air or other such gas or fluidto the right through the horizontal section 601 of the tubing 600,around the bend in the tubing and ina vertical direction down thesection of the tubing 602 to the exhaust tube 603. When the flow of airreaches the exhaust tube 603, its motion is changed from the verticaldirection to the horizontal direction. Thence, it passes along theexhaust tube 603 out of the apparatus.

A fluid ejecting nozzle 610 is centrally located Within the opening ofthe tubing section 601 at its left extremity. The nozzle ejects fluid tothe right through the tube 610 in the same direction with the stream ofair passing through the tubing. The nozzle 610 is maintained in thisposition by a fluid supplying tube 611 which is appropriately fixed tothe wall of the tubing 601 by an appropriate fitting 612 at the point atwhich it passes therethrough. The nozzle 610 as well as thecommunicating tubing, 611, is made of an electroconductive material.This allows the nozzle 610 to be maintained at a nega tive potential byconnection to a terminal 613. An extension tube 614 connecting with tube611 may provide the nozzle 610 with a supply of a pigment solution ordyeing fluid. For example, if it is desirable to coat particles with awater soluble dye, a water solution of Prussian blue, eosine (yellow) orfluorescein (green) may be used.

The dye solution may be drawn from the nozzle 610 by the reducedpressure caused by the flow of air past it, by maintaining a suflicientpressure head on the dyeing fluid by locating a fluid reservoir at asufficient elevation above nozzle 610 or by any conventional pumpingmeans.

A particle ejecting nozzle 615 is radially positioned by attachment tothe Wall of the section of tubing 601. The nozzle 615 is positioned tothe right of nozzle 610 so that it ejects particles into the path of thedye mist from nozzle 610. Nozzle 615 is also composed of material whichis electroconductive so that it may be maintained at a positivepotential by connection to a terminal 616.

Further along the section of the tubing 601 to the right of nozzle 610and 615 an induction heating coil 620 is wound around the outside of thetubing 601. The ends of the winding 620. are joined to terminals 621supplied with radio frequency current. i

The apparatus operates as follows to coat magnetically attractableparticles. As already explained, a stream of air is drawn through thetube 600 past the centrally located nozzle 610 which emits a fine sprayof pigment or dye fluid. Because the fluid sprayed from the nozzle 610is negatively charged, a fine spray or mist is produced which has minutedroplets all bearing the same charge. The similarly charged particlesremain separated into fine particles because they repel each other.

The powder particles injected into the stream of dyebearing mist areeach charged positively by passing through the nozzle 615 connected tothe positive terminal 616. These fine powder particles also tend toseparate allowing each to be fully exposed to the dye mist. There is anattraction between the pigment or dye bearing droplets and the powderedmagnetizable particles because of the opposite charges upon each. Thisaffinity provides means for efiiciently and individually coating each ofthe powdered particles.

The coated particles pass to the right along the tube 601, carried alongby the stream of air and pass through the section of the tubingsurrounded by the induction heating coil 620. The conduction currents oreddy currents induced in the magnetically attractable particles, due tothe radio frequency field produced by the coil 62 0, sutficiently heateach particle to dry its coating of dye or pigment. The coatedparticles, which are now dry, are deflected in a downward direction asthey pass around the elbow in the tube 600. They continue in thedownward direction until they are caught by the pan 604. These particleswill not pass out through the exhaust tube 603 because their inertiaresists deflection from the vertical to the horizontal direction.However, airborne substances, such as dye material not deposited in theabove process on powdered particles, are of lesser mass than thepowdered particles, and are drawn out through the exhaust tube 603. Thismeans provides a suitable device for separating undesired substancesfrom the coated powdered particles.

While this invention has been described and illustrated with referenceto a specific embodiment, it is to be understood that the invention iscapable of various modifications and applications, not departingessentially from the spirit thereof, which will become apparent to thoseskilled in the art.

What is claimed is:

1. In an apparatus utilizing magnetically attractable particles totransfer intelligence to a receiving strip, a cylindrical body havingperipheral surface areas of selected magnetic polarization, a suspensionchamber partially enclosed by a portion of the peripheral surface ofsaid cylindrical body, a baffling structure forming a euculating fluidpath within said suspension chamber tangential to a portion of theperipheral surface of said cylindrical body, a blower unit situated inthe circulating fluid path formed by said baffling structure, a storagechamber situated adjacent to said suspension chamber adapted to storemagnetically attractable particles, a feeding device comprising adriving motor and a feed worm situated in said storage chamber havingone extremity protruding into said suspension chamber and the otherextremity rotated by said driving motor, a density measuring apparatusresponsive to fluid suspensions existing within said suspension chambercontrolling the driving motor of said feeding device, a structureadapted to rotatably mount said cylindrical body for tangential contactof its peripheral surface areas with a continuously moving intelligencereceiving strip, a pressure roller adapted to apply compressive force atthe locations where said cylindrical body contacts said intelligencereceiving strip, and a source of power rotating said cylindrical body.

particles, a cylindrical body having peripheral surface areas ofselected magnetic polarization, a suspension chamber partially enclosedby a portion of the peripheral 2. In an apparatus utilizing magneticallyattractable surface of said cylindrical body, a baflling structureforming a circulating fluid path within said suspension chambertangential to a portion of the peripheral surface of said cylindricalbody, a blower unit situated in the circulating fluid path formed bysaid baffling structure, a reservoir member situated adjacent to saidsuspension chamber adapted to store magnetically attractable particles,a feeding device comprising a driving motor and a helically ridged rodsituated in said reservoir member having one extremity protruding intosaid suspension chamber and the other extremity rotated by said drivingmotor, a density measuring apparatus responsive to fluid suspensionsexisting within said suspension chamber exciting the driving motor ofsaidfeeding device, a structure rotatably supporting said cylindricalbody, and driving connection to said blower unit, said feeding deviceand said cylindrical body.

3. In a system for reproducing a visual record; a device for scanningthe record comprising a photoelectric transducer, an electric signalgenerating network, a modulating network comprising a transformer andsignal clipping devices, the primary of said transformer being connectedtosaid signal generating network, an electromagnetic transducer forrecording on a magnetic recording medium, means including said signalclipping devices coupling the secondary of said transformer to saidelectromagnetic transducer, and means coupling the output of saidphotoelectric transducer to said signal clipping devices to modulate theclipping threshold of said devices in accordance with said photoelectrictransducer output.

4. A magnetic printer for reproducing copies of a visual recordcomprising, a photoelectric scanner for scanning the visual record to bereproduced and for producing electric signals characteristic of thevisual record, a magnetizable member having a finite surface area, anelectromagnetic transducer communicating with the surface of saidmagnetizable member and connected to receive the output of saidphotoelectric scanner, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer in synchronismwith the scanning action of said photoelectric scanner whereby amagnetic image of said visual record is traced out on the surface ofsaid magnetizable member, a source of magnetically attractable powder,means for dusting the image bearing surface of said magnetizable memberwith said powder, a print receiving strip member, means for roll-ingsaid print receiving strip across the dusted image surface of saidmagnetizable member thereby to effect transfer of a visual image to theprint receiving strip, and a liquid atomizer adapted to spray said printreceiving member before it contacts said magnetizable member.

5. A magnetic printer for reproducing copies of a visual recordcomprising, a photoelectric scanner for scanning the visual record to bereproduced and for producing electric signals characteristic of thevisual record, a magnetizable member having a finite surface area, anelectromagnetic transducer communicating with the surface of saidmagnetizable member and connected to receive the output of saidphotoelectric scanner, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer in synchronismwith the scanning action of said photoelectric scanner whereby amagnetic image of said visual record is traced out on the surface ofsaid magnetizable member, a source of magnetically attractable powder,means for dusting the image hearing surface of said magnetizable memberwith said powder, a print receiving strip member, means for rolling saidprint receiving strip across the dusted image surface of saidmagnetizable member thereby toeffect transfer of a visual image to theprint receiving strip, and a magnetic stripping device for removingexcess magnetic powder from said print receiving strip after it hascontacted said magnetizable member.

6. In an apparatus utilizing magnetically attractable particles totransfer intelligence to a receiving strip, a

body having peripheral surface areas of selected magnetic polarization,a suspension chamber partially enclosed by a portion of the peripheralsurface of said body, a bafiiing structure forming a circulating fluidpath within said suspension chamber tangential to a portion of theperipheral surface of said body, a blower unit situated in thecirculating fluid path formed by said bafliing structure, a storagechamber situated adjacent to said suspension chamber adapted to storemagnetically attractable particles, a feeding device comprising adriving motor and a feed worm situated in said storage chamber havingone extremity protruding into said suspension chamber and the otherextremity rotated by said driving motor, a density measuring apparatusresponsive to fluid suspensions existing within said suspension chambercontrolling the driving motor of said feeding device, a structureadapted to mount said body for tangential contact of its peripheralsurface areas with a continuously moving intelligence receiving strip,and a pressure roller adapted to apply compressive force at thelocations where said body contacts said intelligence receiving strip.

7. In an apparatus utilizing magnetically attractable particles, a bodyhaving peripheral surface areas of selected magnetic polarization, asuspension chamber partially enclosed by a portion of the peripheralsurface of said body, a baffling structure forming a circulating fluidpath within said suspension chamber tangential to a portion of theperipheral surface of said cylindrical body, a blower unit situated inthe circulating fluid path formed by said bafiiing structure, areservoir member situated adjacent to said suspension chamber adapted tostore magnetically attractable particles, a feeding device comprising adriving motor and a helically ridged rod situated in said reservoirmember having one extremity protruding into said suspension chamber andthe other extremity rotated by said driving motor, a density measur ingapparatus responsive to fluid suspensions existing within saidsuspension chamber for exciting the driving motor of said feedingdevice, a structure supporting said cylindrical body, and drivingconnection to said blower unit, said feeding device and said body.

8. A magnetic printer for reproducing copies of a visual recordcomprising a photoelectric scanner for scanning the visual record to bereproduced and for producing electric signals characteristic of thevisual record, a magnetizable member having a finite surface area, anelectromagnetic transducer communicating with the surface of saidmagnetizable member and connected to receive the output of saidphotoelectric scanner, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer in synchronismwith the scanning action of said photoelectric scanner whereby amagnetic image of said visual record is traced out on the surface ofsaid magnetizable member, means for dusting the image bearing surface ofsaid magnetizable member with magnetically attractable powder, means forrolling a print receiving strip member across the dusted image surfaceof said magnetizable member thereby to effect transfer of a visual imageto the print receiving strip, and a liquid atomizer adapted to spraysaid print receiving member before it contacts said magnetizable member.

9. A magnetic printer for reproducing copies of a visual recordcomprising a photoelectric scanner for scanning the visual record to bereproduced and for producing electric signals characteristic !of thevisual record, a magnetizable member having a finite surface area, anelectromagnetic transducer communicating with the surface of saidmagnetizable member and connected to receive the output of saidphotoelectric scanner, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer in synchronismwith the scanning action of said photoelectric scanner whereby amagnetic image of said visual record is traced out on the surface ofsaid magnetizable member, means for dusting the image bearing surface ofsaid magnetizable member with magnetically attractable powder, means forrolling a print receiving strip member across the dusted image surfaceof said magnetizable member thereby to effect transfer of a visual imageto the print receiving strip member, and a magnetic stripping device forremoving excess magnetic powder from said print receiving strip after ithas contacted said magnetizable member.

10. A magnetic printer for reproducing copies of a visual recordcomprising a photoelectric scanner for scanning the visual record to bereproduced and for producing electric signals characteristic of thevisual record, a magnetizable member having a finite surface area, anelectromagnetic transducer communicating with the surface of saidmagnetizable member and connected to receive the output of saidphotoelectric scanner, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer in synchronismwith the scanning action of said photoelectric scanner whereby amagnetic image of said visual record is traced out on the surface ofsaid magnetizable member, means for dusting the image bearing surface ofsaid magnetizable member with magnetically attractable powder, means forrolling a print receiving strip member across the dusted image surfaceof said magnetizable member thereby to effect transfer of a visual imageto the print receiving strip, a magnetic stripping device for removingexcess magnetic powder from said print receiving strip after it hascontacted said magnetizable member, and a liquid atomizer adapted tospray said print receiving member before it contacts said magnetizablemember.

11. A magnetic printer comprising means for producing electric signalscharacteristic of the information to be reproduced, a magnetizablemember having a finite surface area, an electromagnetic transducercommunicating with the surface of said magnetizable member and connectedto receive said electric signals, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer whereby amagnetic image of the information to be reproduced is traced out on thesurface of said magnetizable member, means for dusting the image bearingsurface of said magnetizable member with magnetically attractablepowder, means for rolling a print receiving strip member across thedusted image surface of said magnetizable member thereby to effecttransfer of a visual image to the print receiving strip, and a liquidatomizer adapted to spray said print receiving member before it contactssaid magnetizable member.

12. A magnetic printer comprising means for producing electric signalscharacteristic of the information to be reproduced, a magnetizablemember having a finite surface area, an electromagnetic transducercommunicating with the surface of said magnetizable member and connectedto receive said electric signals, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer whereby amagnetic image of the information to be reproduced is traced out on thesurface of said magnetizable member, means for dusting the image bearingsurface of said magnetizable member with magnetically attractablepowder, means for rolling a print receiving strip member acnoss thedusted image surface of said magnetizable member thereby to eifecttransfer of a visual image to the print receiving strip member, and amagnetic stripping device for removing excess magnetic powder from saidprint receiving strip after it has contacted said magnetizable member.

13. A magnetic printer comprising means for producing electric signalscharacteristic of the information to be reproduced, a magnetizablemember having a finite surface area, an electromagnetic transducercommunicating with the surface of said magnetizable member and connectedto receive said electric signals, means for scanning the surface of saidmagnetizable member with said electromagnetic transducer whereby amagnetic image of the information to be reproduced is traced out on thesurface of said magnetizable member, means for dusting the ping devicefor removing excess magnetic powder front image bearing surface of saidmagnetizable member with said print receiving strip after it hascontacted said magmagnetically attractable powder, means for rolling aprint netilable member, and a liquid atomizer adapted t0 p y receivingstrip member across the dusted image surface of said Drillt receivingmember before it contacts Said said magnetizable member thereby toeifect transfer of a 5 netizable member visual image to the printreceiving strip, a magnetic strip- No references cited.

